Iron metabolism: a double-edged sword in the resistance of glioblastoma to therapies

Ferritinophagy: Molecular mechanisms and role in disease

Ferritinophagy is a regulatory pathway of iron homeostasis. It is a process in which nuclear receptor coactivator 4 (NCOA4) carries ferritin to autophagolysosomes for degradation. After ferritin is degraded by autophagy, iron ions are released, which promotes the labile iron pool (LIP) to drive the Fenton reaction to cause lipid peroxidation. Furthermore, ferroptosis promoted by the accumulation of lipid reactive oxygen species (ROS) induced by ferritinophagy can cause a variety of systemic diseases. In clinical studies, targeting the genes regulating ferritinophagy can prevent and treat such diseases. This article describes the key regulatory factors of ferritinophagy and the mechanism of ferritinophagy involved in ferroptosis. It also reviews the damage of ferritinophagy to the body, providing a theoretical basis for further finding clinical treatment methods.

Targeting SIRT3 sensitizes glioblastoma to ferroptosis by promoting mitophagy and inhibiting SLC7A11

Glioblastoma (GBM) cells require large amounts of iron for tumor growth and progression, which makes these cells vulnerable to destruction via ferroptosis induction. Mitochondria are critical for iron metabolism and ferroptosis. Sirtuin-3 (SIRT3) is a deacetylase found in mitochondria that regulates mitochondrial quality and function. This study aimed to characterize SIRT3 expression and activity in GBM and investigate the potential therapeutic effects of targeting SIRT3 while also inducing ferroptosis in these cells. We first found that SIRT3 expression was higher in GBM tissues than in normal brain tissues and that SIRT3 protein expression was upregulated during RAS-selective lethal 3 (RSL3)-induced GBM cell ferroptosis. We then observed that inhibition of SIRT3 expression and activity in GBM cells sensitized GBM cells to RSL3-induced ferroptosis both in vitro and in vivo. Mechanistically, SIRT3 inhibition led to ferrous iron and ROS accumulation in the mitochondria, which triggered mitophagy. RNA-Sequencing analysis revealed that upon SIRT3 knockdown in GBM cells, the mitophagy pathway was upregulated and SLC7A11, a critical antagonist of ferroptosis via cellular import of cystine for glutathione (GSH) synthesis, was downregulated. Forced expression of SLC7A11 in GBM cells with SIRT3 knockdown restored cellular cystine uptake and consequently the cellular GSH level, thereby partially rescuing cell viability upon RSL3 treatment. Furthermore, in GBM cells, SIRT3 regulated SLC7A11 transcription through ATF4. Overall, our study results elucidated novel mechanisms underlying the ability of SIRT3 to protect GBM from ferroptosis and provided insight into a potential combinatorial approach of targeting SIRT3 and inducing ferroptosis for GBM treatment.

Global analysis of iron metabolism-related genes identifies potential mechanisms of gliomagenesis and reveals novel targets

AIMS

This study aimed to investigate key regulators of aberrant iron metabolism in gliomas, and evaluate their effect on biological functions and clinical translational relevance.

METHODS

We used transcriptomic data from multiple cross-platform glioma cohorts to identify key iron metabolism-related genes (IMRGs) based on a series of bioinformatic and machine learning methods. The associations between IMRGs and prognosis, mesenchymal phenotype, and genomic alterations were analyzed in silico. The performance of the IMRGs-based signature in predicting temozolomide (TMZ) treatment sensitivity was evaluated. In vitro and in vivo experiments were used to explore the biological functions of these key IMRGs.

RESULTS

HMOX1, LTF, and STEAP3 were identified as the most essential IMRGs in gliomas. The expression levels of these genes were strongly related to clinicopathological and molecular features. The robust IMRG-based gene signature could be used for prognosis prediction. These genes facilitate mesenchymal transformation, driver gene mutations, and oncogenic alterations in gliomas. The gene signature was also associated with TMZ resistance. HMOX1, LTF, and STEAP3 knockdown in glioma cells significantly reduced cell proliferation, colony formation, migration, and malignant invasion.

CONCLUSION

The study presented a comprehensive view of key regulators underpinning iron metabolism in gliomas and provided new insights into novel therapeutic approaches.

Homeostatic iron regulatory protein drives glioblastoma growth via tumor cell-intrinsic and sex-specific responses

Background

Glioblastoma (GBM) displays alterations in iron that drive proliferation and tumor growth. Iron regulation is complex and involves many regulatory mechanisms, including the homeostatic iron regulator (HFE) gene, which encodes the homeostatic iron regulatory protein. While HFE is upregulated in GBM and correlates with poor survival outcomes, the function of HFE in GBM remains unclear.

Methods

We interrogated the impact of cell-intrinsic Hfe expression on proliferation and survival of intracranially implanted animals through genetic gain- and loss-of-function approaches in syngeneic mouse glioma models, along with in vivo immune assessments. We also determined the expression of iron-associated genes and their relationship to survival in GBM using public data sets and used transcriptional profiling to identify differentially expressed pathways in control compared to Hfe-knockdown cells.

Results

Overexpression of Hfe accelerated GBM proliferation and reduced animal survival, whereas suppression of Hfe induced apoptotic cell death and extended survival, which was more pronounced in females and associated with attenuation of natural killer cells and CD8+ T cell activity. Analysis of iron gene signatures in Hfe-knockdown cells revealed alterations in the expression of several iron-associated genes, suggesting global disruption of intracellular iron homeostasis. Further analysis of differentially expressed pathways revealed oxidative stress as the top pathway upregulated following Hfe loss. Hfe knockdown indeed resulted in enhanced 55Fe uptake and generation of reactive oxygen species.

Conclusions

These findings reveal an essential function for HFE in GBM cell growth and survival, as well as a sex-specific interaction with the immune response.

A closer look at the role of iron in glioblastoma

Glioblastoma (GBM) is among the deadliest malignancies facing modern oncology. While our understanding of certain aspects of GBM biology has significantly increased over the last decade, other aspects, such as the role of bioactive metals in GBM progression, remain understudied. Iron is the most abundant transition metal found within the earth's crust and plays an intricate role in human physiology owing to its ability to participate in oxidation-reduction reactions. The importance of iron homeostasis in human physiology is apparent when examining the clinical consequences of iron deficiency or iron overload. Despite this, the role of iron in GBM progression has not been well described. Here, we review and synthesize the existing literature examining iron's role in GBM progression and patient outcomes, as well as provide a survey of iron's effects on the major cell types found within the GBM microenvironment at the molecular and cellular level. Iron represents an accessible target given the availability of already approved iron supplements and chelators. Improving our understanding of iron's role in GBM biology may pave the way for iron-modulating approaches to improve patient outcomes.

Iron Bioavailability in the Extracellular Environment Is More Relevant Than the Intracellular One in Viability and Gene Expression: A Lesson from Oligodendroglioma Cells

Oligodendroglioma (OG) is a brain tumor that contributes to <1% of brain tumor diagnoses in the pediatric population. Unfortunately, pediatric OG remains without definitive molecular characteristics to aid in diagnosis, and little is known about the tumor microenvironment. Tumor cells' metabolism and proliferation rate are generally higher than those of healthy cells, so their iron demand is also significantly higher. This consideration underlines the great importance of iron for tumor development and progression. In this context, this study aims to evaluate the effect of iron in a cellular in vitro model of human oligodendroglioma brain tumor. Cell morphology, the effect of siderotic medium on cell growth, iron uptake, and the expression of iron-metabolism-related genes were evaluated via optic microscopy, ICP-MS, confocal microscopy, and real-time PCR, respectively. This study underlines the great importance of iron for tumor development and progression and also the possibility of reducing the available iron concentration to determine an antiproliferative effect on OG. Therefore, every attempt can be promising to defeat OG for which there are currently no long-term curative therapies.

Quantitative susceptibility mapping evaluation of glioma

OBJECTIVES

To comprehensively evaluate the glioma using quantitative susceptibility mapping (QSM).

MATERIALS AND METHODS

Forty-two patients (18 women; mean age, 45 years) with pathologically confirmed gliomas were retrospectively included. All the patients underwent conventional and advanced MRI examinations (QSM, DWI, MRS, etc.). Five patients underwent paired QSM (pre- and post-enhancement). Four Visually Accessible Rembrandt Image (VASARI) features and intratumoural susceptibility signal (ITSS) were observed. Three ROIs each were manually drawn separately in the tumour parenchyma with relatively high and low magnetic susceptibility. The association between the tumour's magnetic susceptibility and other MRI parameters was also analysed.

RESULTS

Morphologically, gliomas with heterogeneous ITSS were more similar to high-grade gliomas (p = 0.006, AUC: 0.72, sensitivity: 70%, and specificity: 73%). Heterogeneous ITSS was significantly associated with tumour haemorrhage, necrosis, diffusion restriction, and avid enhancement but did not change between pre- and post-enhanced QSM. Quantitatively, tumour parenchyma magnetic susceptibility had limited value in grading gliomas and identifying IDH mutation status, whereas the relatively low magnetic susceptibility of the tumour parenchyma helped identify oligodendrogliomas in IDH mutated gliomas (AUC = 0.78) with high specificity (100%). The relatively high tumour magnetic susceptibility significantly increased after enhancement (p = 0.039). Additionally, we found that the magnetic susceptibility of the tumour parenchyma was significantly correlated with ADC (r = 0.61) and Cho/NAA (r = 0.40).

CONCLUSIONS

QSM is a promising candidate for the comprehensive evaluation of gliomas, except for IDH mutation status. The magnetic susceptibility of tumour parenchyma may be affected by tumour cell proliferation.

KEY POINTS

• Morphologically, gliomas with a heterogeneous intratumoural susceptibility signal (ITSS) are more similar to high-grade gliomas (p = 0.006; AUC, 0.72; sensitivity, 70%; and specificity, 73%). Heterogeneous ITSS was significantly associated with tumour haemorrhage, necrosis, diffusion restriction, and avid enhancement but did not change between pre- and post-enhanced QSM. • Tumour parenchyma's relatively low magnetic susceptibility helped identify oligodendroglioma with high specificity. • Tumour parenchyma magnetic susceptibility was significantly correlated with ADC (r = 0.61) and Cho/NAA (r = 0.40).

Non-invasive assessment of normal and impaired iron homeostasis in the brain

Strict iron regulation is essential for normal brain function. The iron homeostasis, determined by the milieu of available iron compounds, is impaired in aging, neurodegenerative diseases and cancer. However, non-invasive assessment of different molecular iron environments implicating brain tissue's iron homeostasis remains a challenge. We present a magnetic resonance imaging (MRI) technology sensitive to the iron homeostasis of the living brain (the r1-r2* relaxivity). In vitro, our MRI approach reveals the distinct paramagnetic properties of ferritin, transferrin and ferrous iron ions. In the in vivo human brain, we validate our approach against ex vivo iron compounds quantification and gene expression. Our approach varies with the iron mobilization capacity across brain regions and in aging. It reveals brain tumors' iron homeostasis, and enhances the distinction between tumor tissue and non-pathological tissue without contrast agents. Therefore, our approach may allow for non-invasive research and diagnosis of iron homeostasis in living human brains.

IRP1 mediated ferroptosis reverses temozolomide resistance in glioblastoma via affecting LCN2/FPN1 signaling axis depended on NFKB2

The prognosis of glioblastoma (GBM) patients is poor, and temozolomide (TMZ) resistance has become an important obstacle to its treatment effect. A growing number of researches have revealed the special characteristics of iron metabolism in GBM chemosensitivity. Iron regulatory protein 1 (IRP1) is an important protein for maintaining intracellular iron homeostasis. IRP1 has been indicated to have additional vital roles beyond its conventional metabolic activity, but the underlying mechanisms and biological consequences remain elusive. Here, we unprecedentedly demonstrated that amplifying IRP1 signals can reverse TMZ resistance and suppress tumor growth in vivo via inhibiting NFKB2 in the noncanonical NF-κB signaling pathway. In addition, we identified that NFKB2 affected TMZ sensitivity of GBM by modulating the expression of LCN2 and FPN1. Taken together, this study established a role for the IRP1/NFKB2 pathway in regulating LCN2/FPN1 signaling axis among the progression of TMZ resistance, suggesting a potential innovative GBM therapeutic strategy.

Engineered Salmonella inhibits GPX4 expression and induces ferroptosis to suppress glioma growth in vitro and in vivo

PURPOSE

Glioma is a life-threatening malignancy where conventional therapies are ineffective. Bacterial cancer therapy has shown potential for glioma treatment, in particular, the facultative anaerobe Salmonella has been extensively studied. Meanwhile, ferroptosis is a newly characterized form of cell death. Nevertheless, the role of ferroptosis in Salmonella-induced tumour cell death remains unclear. Therefore, we aim to elucidate whether Salmonella YB1 exerts therapeutic effects via inducing ferroptosis in glioma.

METHODS

Following Salmonella YB1 infection, mRNA sequencing was applied to detect ferroptosis-related gene expression and the levels of reactive oxygen species, malondialdehyde, and glutathione were quantified. Transmission electron microscopy (TEM) was then used to observe the changes in the mitochondrial morphology of glioma cells. The role of ferroptosis in the anti-tumor effect of YB1 was assessed in vivo in mouse tumor xenograft models.

RESULTS

Whole-transcriptome analysis revealed that Salmonella YB1 infection alters ferroptosis-related gene expression in the U87 glioma cell line. Moreover, we found that Salmonella-induced ferroptosis is correlated with reduced levels of glutathione and glutathione peroxidase-4 (GPX4) and increased levels of reactive oxygen species and malondialdehyde in vitro. Meanwhile, TEM revealed that mitochondria are shrunken and mitochondrial membrane density increases in infected glioma cells. Experiments in vivo further showed that tumor growth in the Salmonella-treated group was significantly slower compared to the control and Fer-1 groups. However, Salmonella-induced tumor suppression can be reversed in vivo by Fer-1 treatment.

CONCLUSION

Salmonella YB1 inhibits GPX4 expression and induces ferroptosis to suppress glioma growth. Hence, ferroptosis regulation might represent a promising strategy to improve the efficacy of bacterial cancer therapy.

TFR2 regulates ferroptosis and enhances temozolomide chemo-sensitization in gliomas

Glioma is a common type of brain tumor with high incidence and mortality rates. Iron plays an important role in various physiological and pathological processes. Iron entry into the cell is promoted by binding the transferrin receptor 2 (TFR2) to the iron-transferrin complex. This study was designed to assess the association between TFR2 and ferroptosis in glioma. Lipid peroxidation levels in glioma cells were assessed by determination of lipid reactive oxygen species (ROS), glutathione content, and mitochondrial membrane potential. The effect of TFR2 on TMZ sensitivity was examined by cell viability assays, flow cytometry, and colony formation assays. We found that Low TFR2 expression predicted a better prognosis for glioma patients. And overexpression of TFR2 promoted the production of reactive oxygen species and lipid peroxidation in glioma cells, thereby further promoting ferroptosis. This could be reversed by the ferroptosis inhibitors Fer-1 and DFO (both inhibitors of ferroptosis). Moreover, TFR2 potentiated the cytotoxic effect of TMZ (temozolomide) via activating ferroptosis. In conclusion, we found that TFR2 induced ferroptosis and enhanced TMZ sensitivity in gliomas. Our findings might provide a new treatment strategy for glioma patients and improve their prognosis.

Heat shock protein 27 deficiency promotes ferrous ion absorption and enhances acyl-Coenzyme A synthetase long-chain family member 4 stability to promote glioblastoma cell ferroptosis

BACKGROUND

Glioblastoma is one of the malignant tumors of the central nervous system with high lethality, high disability and low survival rate. Effective induction of its death is one of the existing challenges. In recent studies, heat shock protein 27 (HSP27) has been shown to be associated with ferroptosis; therefore, targeting HSP27 may be a potential therapeutic approach for GBM.

METHODS

Immunohistochemistry and western blot analysis were used to detect the expression of HSP27 in GBM tissues. CCK8, plate clone formation assay, EdU proliferation assay for cell proliferation ability, PI, LDH release assay for cell viability. Reactive oxygen, iron levels, and mitochondrial potential for HSP27 silencing were assayed for ferrotosis in vitro. Western blotting and IP were used to verify the relationship between HSP27 and ACSL4. The effect of knockdown of HSP27 on tumor growth capacity was assessed in an intracranial xenograft model.

RESULTS

HSP27 was significantly highly expressed in GBM. In vitro experiments, knockdown of HSP27 significantly induced ferroptosis in GBM cells. IP and western blot demonstrated a sumo-ization link between HSP27 and ACSL4. In vivo experiments, HSP27 deficiency retarded tumor growth rate by promoting ferroptosis.

CONCLUSIONS

HSP27 deficiency promotes GBM ferroptosis. Targeting HSP27 may serve as a new direction for GBM treatment.

Development and validation of a prognostic prediction model for iron metabolism-related genes in patients with pancreatic adenocarcinoma

Background: Pancreatic adenocarcinoma (PAAD) is one of the most aggressive tumors of the digestive tract, with low surgical resection rate and insensitivity to radiotherapy and chemotherapy. Existing evidence suggests that regulation of ferroptosis can induce PAAD cell death, inhibit tumor growth, and may synergistically improve the sensitivity of other antitumor drugs. However, there is little of systematic research on iron metabolism-related genes in PAAD. In this study, a risk-score system of PAAD iron metabolism-related genes was designed and tested, and verified to be robust. Materials and Methods: The TCGA database was used to download 177 PAAD patients' message RNA (mRNA) expression profiles and clinical characteristics. By identifying dysregulated iron metabolism-related genes between PAAD related tissues and adjacent normal tissues, univariate Cox proportional hazards regression and LASSO regression algorithm were used to establish prognostic risk-score system and construct nomogram to estimate the 1-, 2-, 3-year survival in PAAD patients. Finally, selected genes were validated by quantitative PCR (q-PCR). Results: A 9-gene related to iron metabolism risk-score system of PAAD was constructed and validated. The clinicopathological characteristics of age, histologic grade, pathologic stage, T stage, residual tumor, and primary therapy outcome were all worse in patients with a higher risk-score. Further, immunohistochemistry results of SLC2A1, MBOAT2, XDH, CTSE, MOCOS, and ATP6V0A4 confirmed that patients with higher expression are more malignant. Then, a nomogram with 9-gene risk score system as a separate clinical factor was utilized to foretell the 1-, 2-, 3-year overall survival rate of PAAD patients. Results of q-PCR showed that 8 of the 9 genes screened were significantly up-regulated in at least one PAAD cell line, and one gene was significantly down-regulated in three PAAD cell lines. Conclusion: To conclude, we generated a nine-gene system linked to iron metabolism as an independent indicator for predicting PAAD prognosis, therefore presenting a possible prognostic biomarker and potential treatment targets for PAAD.

Molecular mechanisms of ferroptosis and the potential therapeutic targets of ferroptosis signaling pathways for glioblastoma

Ferroptosis is a newly identified form of cell death that differs from autophagy, apoptosis and necrosis, and its molecular characteristics include iron-dependent lipid reactive oxygen species accumulation, mitochondrial morphology changes, and membrane permeability damage. These characteristics are closely related to various human diseases, especially tumors of the nervous system. Glioblastoma is the most common primary malignant tumor of the adult central nervous system, and the 5-year survival rate is only 4%-5%. This study reviewed the role and mechanism of ferroptosis in glioblastoma and the research status and progress on ferroptosis as a potential therapeutic target. The mechanism of ferroptosis is related to the intracellular iron metabolism level, lipid peroxide content and glutathione peroxidase 4 activity. It is worth exploring how ferroptosis can be applied in disease treatment; however, the relation between ferroptosis and other apoptosis methods is poorly understood and methods of applying ferroptosis to drug-resistant tumors are insufficient. Ferroptosis is a promising therapeutic target for glioblastoma. In-depth studies of its mechanism of action in glioblastoma and applications for clinical treatment are expected to provide insights for glioblastoma patients.

Potential of six-transmembrane epithelial antigen of the prostate 4 as a prognostic marker for colorectal cancer

BACKGROUND

Immune cells play a role in the regulation of tumor cell behavior, and accumulating evidence supports their significance in predicting outcomes and therapeutic efficacy in colorectal cancers (CRC). Human six-transmembrane epithelial antigen of the prostate (STEAP) proteins have been recognized and utilized as promising targets for cell- and antibody-based immunotherapy. One STEAP family member, STEAP4, is expected to be an attractive biomarker for the immunotherapy of prostate and breast cancer. However, the immunotherapeutic role of STEAP4 for colorectal carcinomas has not been demonstrated.

AIM

To explore the expression pattern of STEAPs in CRC and their relationship with immune infiltration, and investigate the potential utilization of STEAPs as novel prognostic indicators in colorectal carcinomas.

METHODS

The expression level of STEAPs in CRC was evaluated using various open-resource databases and online tools to explore the expression characteristics and prognostic significance of STEAPs, as well as their correlation with immune-related biomarkers, such as immune infiltration. Immunohistochemical (IHC) experiments were subsequently performed to verify the database conclusions.

RESULTS

The levels of STEAPs in CRC were inconsistent. The expression of STEAPs 1-3 in CRC was not significantly different from that in normal tissues. However, STEAP4 mRNA levels were significantly lower in CRC than in normal tissue and were positively correlated with immune-related biomarkers, such as immune cell infiltration, immune stimulation, major histocompatibility complex levels, and chemokines. Interestingly, the expression of STEAP4 in microsatellite instability-high CRC subtype was higher than that in microsatellite stability subtype. IHC staining was performed on colon cancer tissue samples and showed that high expression of STEAP4 in adjacent tissues positively correlated with immune-related biomarkers, including MLH1, MLH6, and PMS2, but negatively correlated with programmed death ligand 1, to varying degrees.

CONCLUSION

Our results provide an analysis of the expression of STEAP family members in CRC. Among different STEAP family members, STEAP4 plays a different role in CRC compared to STEAPs 1-3. In CRC, STEAP4 expression is not only lower than that in normal tissues, but it is also positively correlated with immune infiltration and immune-related biomarkers. These findings suggest that STEAP4 may be a potential biomarker for predicting CRC immune infiltration status.

Emerging roles of ferroptosis in glioma

Glioma is the most common primary malignant tumor in the central nervous system, and directly affects the quality of life and cognitive function of patients. Ferroptosis, is a new form of regulated cell death characterized by iron-dependent lipid peroxidation. Ferroptosis is mainly due to redox imbalance and involves multiple intracellular biology processes, such as iron metabolism, lipid metabolism, and antioxidants synthesis. Induction of ferroptosis could be a new target for glioma treatment, and ferroptosis-related processes are associated with chemoresistance and radioresistance in glioma. In the present review, we provide the characteristics, key regulators and pathways of ferroptosis and the crosstalk between ferroptosis and other programmed cell death in glioma, we also proposed the application and prospect of ferroptosis in the treatment of glioma.

A role for ceruloplasmin in the control of human glioblastoma cell responses to radiation

Background

Glioblastoma (GB) is the most common and most aggressive malignant brain tumor. In understanding its resistance to conventional treatments, iron metabolism and related pathways may represent a novel avenue. As for many cancer cells, GB cell growth is dependent on iron, which is tightly involved in red-ox reactions related to radiotherapy effectiveness. From new observations indicating an impact of RX radiations on the expression of ceruloplasmin (CP), an important regulator of iron metabolism, the aim of the present work was to study the functional effects of constitutive expression of CP within GB lines in response to beam radiation depending on the oxygen status (21% O₂ versus 3% O₂).

Methods and results

After analysis of radiation responses (Hoechst staining, LDH release, Caspase 3 activation) in U251-MG and U87-MG human GB cell lines, described as radiosensitive and radioresistant respectively, the expression of 9 iron partners (TFR1, DMT1, FTH1, FTL, MFRN1, MFRN2, FXN, FPN1, CP) were tested by RTqPCR and western blots at 3 and 8 days following 4 Gy irradiation. Among those, only CP was significantly downregulated, both at transcript and protein levels in the two lines, with however, a weaker effect in the U87-MG, observable at 3% O₂. To investigate specific role of CP in GB radioresistance, U251-MG and U87-MG cells were modified genetically to obtain CP depleted and overexpressing cells, respectively. Manipulation of CP expression in GB lines demonstrated impact both on cell survival and on activation of DNA repair/damage machinery (γH2AX); specifically high levels of CP led to increased production of reactive oxygen species, as shown by elevated levels of superoxide anion, SOD1 synthesis and cellular Fe2 + .

Conclusions

Taken together, these in vitro results indicate for the first time that CP plays a positive role in the efficiency of radiotherapy on GB cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09808-6.

TRIM7 modulates NCOA4-mediated ferritinophagy and ferroptosis in glioblastoma cells

Objective

Glioblastoma is one of the most common intracranial malignant tumors with an unfavorable prognosis, and iron metabolism as well as ferroptosis are implicated in the pathogenesis of glioblastoma. The present study aims to decipher the role and mechanisms of tripartite motif-containing protein 7 (TRIM7) in ferroptosis and glioblastoma progression.

Methods

Stable TRIM7-deficient or overexpressing human glioblastoma cells were generated with lentiviral vectors, and cell survival, lipid peroxidation and iron metabolism were evaluated. Immunoprecipitation, protein degradation and ubiquitination assays were performed to demonstrate the regulation of TRIM7 on its candidate proteins.

Results

TRIM7 expression was elevated in human glioblastoma cells and tissues. TRIM7 silence suppressed growth and induced death, while TRIM7 overexpression facilitated growth and inhibited death of human glioblastoma cells. Meanwhile, TRIM7-silenced cells exhibited increased iron accumulation, lipid peroxidation and ferroptosis, which were significantly reduced by TRIM7 overexpression. Mechanistically, TRIM7 directly bound to and ubiquitinated nuclear receptor coactivator 4 (NCOA4) using K48-linked chains, thereby reducing NCOA4-mediated ferritinophagy and ferroptosis of human glioblastoma cells. Moreover, we found that TRIM7 deletion sensitized human glioblastoma cells to temozolomide therapy.

Conclusion

We for the first time demonstrate that TRIM7 modulates NCOA4-mediated ferritinophagy and ferroptosis in glioblastoma cells, and our findings provide a novel insight into the progression and treatment for human glioblastoma.

MicroRNA delivery systems in glioma therapy and perspectives: A systematic review

Gliomas are the deadliest of all primary brain tumors, and they constitute a serious global health problem. MicroRNAs (miRNAs) are gene expression regulators associated with glioma pathogenesis. Thus, miRNAs represent potential therapeutic agents for treating gliomas. However, miRNAs have not been established as part of the regular clinical armamentarium. This systemic review evaluates current molecular and pre-clinical studies with the aim of defining the most appealing supramolecular platform for administering therapeutic miRNA to patients with gliomas. An integrated analysis suggested that cationic lipid nanoparticles, functionalized with octa-arginine peptides, represent a potentially specific, practical, non-invasive intervention for treating gliomas. This supramolecular platform allows loading both hydrophilic (miRNA) and hydrophobic (anti-tumor drugs, like temozolomide) molecules. This systemic review is the first to describe miRNA delivery systems targeted to gliomas that integrate several types of molecules as active ingredients. Further experimental validation is warranted to confirm the practical value of miRNA delivery systems.

Ameliorating potential of curcumin and its analogue in central nervous system disorders and related conditions: A review of molecular pathways

Curcumin, isolated from turmeric (Curcuma longa L.) is one of the broadly studied phytomolecule owing to its strong antioxidant and anti-inflammatory potential and has been considered a promising therapeutic candidate in a wide range of disorders. Considering, its low bioavailability, different curcumin analogs have been developed to afford desired pharmacokinetic profile and therapeutic outcome in varied pathological states. Several preclinical and clinical studies have indicated that curcumin ameliorates mitochondrial dysfunction, inflammation, oxidative stress apoptosis-mediated neural cell degeneration and could effectively be utilized in the treatment of different neurodegenerative diseases. Hence, in this review, we have summarized key findings of experimental and clinical studies conducted on curcumin and its analogues with special emphasis on molecular pathways, viz. NF-kB, Nrf2-ARE, glial activation, apoptosis, angiogenesis, SOCS/JAK/STAT, PI3K/Akt, ERK1/2 /MyD88 /p38 MAPK, JNK, iNOS/NO, and MMP pathways involved in imparting ameliorative effects in the therapy of neurodegenerative disorders and associated conditions.

Inhibitory effects of temozolomide on glioma cells is sensitized by RSL3-induced ferroptosis but negatively correlated with expression of ferritin heavy chain 1 and ferritin light chain

Invasive growth of glioblastoma makes residual tumor unremovable by surgery and leads to disease relapse. Temozolomide is widely used first-line chemotherapy drug to treat glioma patients, but development of temozolomide resistance is almost inevitable. Ferroptosis, an iron-dependent form of non-apoptotic cell death, is found to be related to temozolomide response of gliomas. However, whether inducing ferroptosis could affect invasive growth of glioblastoma cells and which ferroptosis-related regulators were involved in temozolomide resistance are still unclear. In this study, we treated glioblastoma cells with RSL3, a ferroptosis inducer, in vitro (cell lines) and in vivo (subcutaneous and orthotopic animal models). The treated glioblastoma cells with wild-type or mutant IDH1 were subjected to RNA sequencing for transcriptomic profiling. We then analyze data from our RNA sequencing and public TCGA glioma database to identify ferroptosis-related biomarkers for prediction of prognosis and temozolomide resistance in gliomas. Analysis of transcriptome data from RSL3-treated glioblastoma cells suggested that RSL3 could inhibit glioblastoma cell growth and suppress expression of genes involved in cell cycle. RSL3 effectively reduced mobility of glioblastoma cells through downregulation of critical genes involved in epithelial-mesenchymal transition. Moreover, RSL3 in combination with temozolomide showed suppressive efficacy on glioblastoma cell growth, providing a promising therapeutic strategy for glioblastoma treatment. Although temozolomide attenuated invasion of glioblastoma cells with mutant IDH1 more than those with wild-type IDH1, the combination of RSL3 and temozolomide similarly impaired invasive ability of glioblastoma cells in spite of IDH1 status. Finally, we noticed that both ferritin heavy chain 1 and ferritin light chain predicted unfavorable prognosis of glioma patients and were significantly correlated with mRNA levels of methylguanine methyltransferase as well as temozolomide resistance. Altogether, our study provided rationale for combination of RSL3 with temozolomide to suppress glioblastoma cells and revealed ferritin heavy chain 1 and ferritin light chain as biomarkers to predict prognosis and temozolomide resistance of glioma patients.

Basal Ganglia Iron Content Increases with Glioma Severity Using Quantitative Susceptibility Mapping: A Potential Biomarker of Tumor Severity

BACKGROUND AND PURPOSE

Gliomas have been found to alter iron metabolism and transport in ways that result in an expansion of their intracellular iron compartments to support aggressive tumor growth. This study used deep neural network trained quantitative susceptibility mapping to assess basal ganglia iron concentrations in glioma patients.

MATERIALS AND METHODS

Ninety-two patients with brain lesions were initially enrolled in this study and fifty-nine met the inclusion criteria. Susceptibility-weighted images were collected at 3.0 T and used to construct quantitative susceptibility maps via a deep neural network-based method. The regions of interest were manually drawn within basal ganglia structures and the mean voxel intensities were extracted and averaged across multiple slices. One-way ANCOVA tests were conducted to compare the susceptibility values of groups of patients based on tumor grade while controlling for age, sex, and tumor type.

RESULTS

The mean basal ganglia susceptibility for patients with grade IV tumors was higher than that for patients with grade II tumors (p = 0.00153) and was also higher for patients with grade III tumors compared to patients with grade II tumors (p = 0.020), after controlling for age, sex, and tumor type. Patient age influenced susceptibility values (p = 0.00356), while sex (p = 0.69) and tumor type (p = 0.11) did not.

CONCLUSIONS

The basal ganglia iron content increased with glioma severity. Basal ganglia iron levels may thus be a useful biomarker in glioma prognosis and treatment, especially with regard to iron-based cancer therapies.

Ferroptosis Involvement in Glioblastoma Treatment

Glioblastoma multiforme (GBM) is one of the deadliest brain tumors. Current standard therapy includes tumor resection surgery followed by radiotherapy and chemotherapy. Due to the tumors invasive nature, recurrences are almost a certainty, giving the patients after diagnosis only a 12–15 months average survival time. Therefore, there is a dire need of finding new therapies that could potentially improve patient outcomes. Ferroptosis is a newly described form of cell death with several implications in cancer, among which GBM. Agents that target different molecules involved in ferroptosis and that stimulate this process have been described as potentially adjuvant anti-cancer treatment options. In GBM, ferroptosis stimulation inhibits tumor growth, improves patient survival, and increases the efficacy of radiation and chemotherapy. This review provides an overview of the current knowledge regarding ferroptosis modulation in GBM.

Harnessing oxidative stress for anti-glioma therapy

Glioma cells use intermediate levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) for growth and invasion, and suppressing these reactive molecules thus may compromise processes that are vital for glioma survival. Increased oxidative stress has been identified in glioma cells, in particular in glioma stem-like cells. Studies have shown that these cells harbor potent antioxidant defenses, although endogenous protection against nitrosative stress remains understudied. The enhancement of oxidative or nitrosative stress offers a potential target for triggering glioma cell death, but whether oxidative and nitrosative stresses can be combined for therapeutic effects requires further research. The optimal approach of harnessing oxidative stress for anti-glioma therapy should include the induction of free radical-induced oxidative damage and the suppression of antioxidant defense mechanisms selectively in glioma cells. However, selective induction of oxidative/nitrosative stress in glioma cells remains a therapeutic challenge, and research into selective drug delivery systems is ongoing. Because of multifactorial mechanisms of glioma growth, progression, and invasion, prospective oncological therapies may include not only therapeutic oxidative/nitrosative stress but also inhibition of oncogenic kinases, antioxidant molecules, and programmed cell death mediators.

Predictive potential of STEAP family for survival, immune microenvironment and therapy response in glioma

Glioma is the most commonly diagnosed primary tumor of central nervous system. Previous studies found that the six-transmembrane epithelial antigen of prostate (STEAP) family can regulate the biological behaviors of several cancers. However, the role of STEAP family in glioma remains unclear. Here, we systematically evaluated the relationship between STEAP family and prognosis of glioma patients in multiple cohorts. The analysis showed that dysregulation of STEAP family may affect cancer-immunity cycle, immune infiltration and phenotypes resulting in an immunosuppressive microenvironment in glioma. To accurately predict the prognosis of glioma patients, gene-based risk models were established based on the expression of STEAP1, 2 and 3. Multivariate and univariate Cox analyses demonstrated that the risk models could independently predict the prognosis of glioma. Finally, chemotherapy and immune therapy responses for high- and low-risk patients were predicted. In conclusion, this study systematically analyzed the role of STEAP family in glioma and established a model for predicting therapy response in patients with glioma.

Identification of Iron Metabolism-Related Genes as Prognostic Indicators for Lower-Grade Glioma

Lower-grade glioma (LGG) is characterized by genetic and transcriptional heterogeneity, and a dismal prognosis. Iron metabolism is considered central for glioma tumorigenesis, tumor progression and tumor microenvironment, although key iron metabolism-related genes are unclear. Here we developed and validated an iron metabolism-related gene signature LGG prognosis. RNA-sequence and clinicopathological data from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) were downloaded. Prognostic iron metabolism-related genes were screened and used to construct a risk-score model via differential gene expression analysis, univariate Cox analysis, and the Least Absolute Shrinkage and Selection Operator (LASSO)-regression algorithm. All LGG patients were stratified into high- and low-risk groups, based on the risk score. The prognostic significance of the risk-score model in the TCGA and CGGA cohorts was evaluated with Kaplan-Meier (KM) survival and receiver operating characteristic (ROC) curve analysis. Risk- score distributions in subgroups were stratified by age, gender, the World Health Organization (WHO) grade, isocitrate dehydrogenase 1 (IDH1) mutation status, the O6-methylguanine-DNA methyl-transferase (MGMT) promoter-methylation status, and the 1p/19q co-deletion status. Furthermore, a nomogram model with a risk score was developed, and its predictive performance was validated with the TCGA and CGGA cohorts. Additionally, the gene set enrichment analysis (GSEA) identified signaling pathways and pathological processes enriched in the high-risk group. Finally, immune infiltration and immune checkpoint analysis were utilized to investigate the tumor microenvironment characteristics related to the risk score. We identified a prognostic 15-gene iron metabolism-related signature and constructed a risk-score model. High risk scores were associated with an age of > 40, wild-type IDH1, a WHO grade of III, an unmethylated MGMT promoter, and 1p/19q non-codeletion. ROC analysis indicated that the risk-score model accurately predicted 1-, 3-, and 5-year overall survival rates of LGG patients in the both TCGA and CGGA cohorts. KM analysis showed that the high-risk group had a much lower overall survival than the low-risk group (P < 0.0001). The nomogram model showed a strong ability to predict the overall survival of LGG patients in the TCGA and CGGA cohorts. GSEA analysis indicated that inflammatory responses, tumor-associated pathways, and pathological processes were enriched in high-risk group. Moreover, a high risk score correlated with the infiltration immune cells (dendritic cells, macrophages, CD4+ T cells, and B cells) and expression of immune checkpoint (PD1, PDL1, TIM3, and CD48). Our prognostic model was based on iron metabolism-related genes in LGG, can potentially aid in LGG prognosis, and provides potential targets against gliomas.

Complementary and alternative medicine in children with diffuse intrinsic pontine glioma-A SIOPE DIPG Network and Registry study

INTRODUCTION

Diffuse intrinsic pontine glioma (DIPG) is a rare and aggressive childhood brainstem malignancy with a 2-year survival rate of <10%. This international survey study aims to evaluate the use of complementary and alternative medicine (CAM) in this patient population.

METHODS

Parents and physicians of patients with DIPG were asked to participate in a retrospective online survey regarding CAM use during time of illness.

RESULTS

Between January and May 2020, 120 parents and 75 physicians contributed to the online survey. Most physicians estimated that <50% of their patients used CAM, whereas 69% of the parents reported using CAM to treat their child during time of illness. Cannabis was the most frequently used form of CAM, followed by vitamins and minerals, melatonin, curcumin, and boswellic acid. CAM was mainly used with the intention of direct antitumor effect. Other motivations were to treat side effects of chemotherapy or to increase comfort of the child. Children diagnosed from 2016 onwards were more likely to use CAM (χ²  = 6.08, p = .014). No significant difference was found between CAM users and nonusers based on ethnicity (χ²  = 4.18, p = .382) or country of residence (χ²  = 9.37, p = .154). Almost 50% of the physicians do not frequently ask their patients about possible CAM use.

CONCLUSION

This survey demonstrates that worldwide, a considerable number of patients with DIPG use CAM. Physicians should be more aware of potential CAM use and actively discuss the topic. In addition, more research is needed to gain knowledge about possible anticancer effects of CAM and (positive/negative) interactions with conventional therapies.

The Macrophage Iron Signature in Health and Disease

Throughout life, macrophages are located in every tissue of the body, where their main roles are to phagocytose cellular debris and recycle aging red blood cells. In the tissue niche, they promote homeostasis through trophic, regulatory, and repair functions by responding to internal and external stimuli. This in turn polarizes macrophages into a broad spectrum of functional activation states, also reflected in their iron-regulated gene profile. The fast adaptation to the environment in which they are located helps to maintain tissue homeostasis under physiological conditions.

Adaptive Changes Allow Targeting of Ferroptosis for Glioma Treatment

Ferroptosis is a type of regulated cell death that plays an essential role in various brain diseases, including cranial trauma, neuronal diseases, and brain tumors. It has been reported that cancer cells rely on their robust antioxidant capacity to escape ferroptosis. Therefore, ferroptosis exploitation could be an effective strategy to prevent tumor proliferation and invasion. Glioma is a common malignant craniocerebral tumor exhibiting complicated drug resistance and survival mechanisms, resulting in a high mortality rate and short survival time. Recent studies have determined that metabolic alterations in glioma offer exploitable therapeutic targets. These metabolic alterations allow targeted therapy to achieve some initial efficacy but have failed to inhibit glioma growth, invasion, and drug resistance effectively. It has been proposed that the reason for the high malignancy and drug resistance observed with glioma is that these tumors can effectively evade ferroptosis. Ferroptosis-inducing drugs were found to exert a positive effect by targeting this particular characteristic of glioma cells. Moreover, gliomas develop enhanced drug resistance through anti-ferroptosis mechanisms. In this study, we provided an overview of the mechanisms by which glioma aggressiveness and drug resistance are mediated by the evasion of ferroptosis. This information might provide new targets for glioma therapy as well as new insights and ideas for future research.

Dioscin induces ferroptosis and synergistic cytotoxicity with chemotherapeutics in melanoma cells

In this study, we evaluated the anti-tumor effects of dioscin, a steroidal saponin, on melanoma cells. Dioscin significantly inhibited cell viability and induced cell death of melanoma cells in a time- and dose- dependent manner. Furthermore, dioscin increased the concentration of intracellular ferrous irons, MDA and ROS. This effect could be inhibited by L-g-glutamyl-p-nitroanilide (GPNA), compound 968 and ferroptosis inhibitor ferrostatin-1 (Fer-1). Furthermore, dioscin induced ferroptosis by affecting the expression of transferrin and ferroportin which are regulators of intracellular levels of iron. Finally, dioscin in combination with various chemotherapeutic agents showed synergistic effects against melanoma cells. Our data suggested that dioscin exerted anti-tumor effects in melanoma cells by inducing ferroptosis. Dioscin alone or with other agents might be applied as a promising strategy to treat melanoma.

The Role of 2-Oxoglutarate Dependent Dioxygenases in Gliomas and Glioblastomas: A Review of Epigenetic Reprogramming and Hypoxic Response

Gliomas are a heterogeneous group of cancers that predominantly arise from glial cells in the brain, but may also arise from neural stem cells, encompassing low-grade glioma and high-grade glioblastoma. Whereas better diagnosis and new treatments have improved patient survival for many cancers, glioblastomas remain challenging with a highly unfavorable prognosis. This review discusses a super-family of enzymes, the 2-oxoglutarate dependent dioxygenase enzymes (2-OGDD) that control numerous processes including epigenetic modifications and oxygen sensing, and considers their many roles in the pathology of gliomas. We specifically describe in more detail the DNA and histone demethylases, and the hypoxia-inducible factor hydroxylases in the context of glioma, and discuss the substrate and cofactor requirements of the 2-OGDD enzymes. Better understanding of how these enzymes contribute to gliomas could lead to the development of new treatment strategies.

Loss of COPZ1 induces NCOA4 mediated autophagy and ferroptosis in glioblastoma cell lines

Dysregulated iron metabolism is a hallmark of many cancers, including glioblastoma (GBM). However, its role in tumor progression remains unclear. Herein, we identified coatomer protein complex subunit zeta 1 (COPZ1) as a therapeutic target candidate which significantly dysregulated iron metabolism in GBM cells. Overexpression of COPZ1 was associated with increasing tumor grade and poor prognosis in glioma patients based on analysis of expression data from the publicly available database The Cancer Genome Atlas (P < 0.001). Protein levels of COPZ1 were significantly increased in GBM compared to non-neoplastic brain tissue samples in immunohistochemistry and western blot analysis. SiRNA knockdown of COPZ1 suppressed proliferation of U87MG, U251 and P3#GBM in vitro. Stable expression of a COPZ1 shRNA construct in U87MG inhibited tumor growth in vivo by ~60% relative to controls at day 21 after implantation (P < 0.001). Kaplan-Meier analysis of the survival data demonstrated that the overall survival of tumor bearing animals increased from 20.8 days (control) to 27.8 days (knockdown, P < 0.05). COPZ1 knockdown also led to the increase in nuclear receptor coactivator 4 (NCOA4), resulting in the degradation of ferritin, and a subsequent increase in the intracellular levels of ferrous iron and ultimately ferroptosis. These data demonstrate that COPZ1 is a critical mediator in iron metabolism. The COPZ1/NCOA4/FTH1 axis is therefore a novel therapeutic target for the treatment of human GBM.

Comprehensive landscape of STEAP family functions and prognostic prediction value in glioblastoma

Glioblastoma (GBM) is the most common, malignant, and deadly primary glioma. Six-transmembrane epithelial antigen of prostate (STEAP) family is involved in tumorigenesis; here, we have explored the biological function and the prognostic value of the STEAP family in GBM. Differentially expressed STEAP genes in tumor and normal samples were screened by using The Cancer Genome Atlas (TCGA) database. Univariate and multivariate Cox regression identified the prognosis-related genes: STEAP2 and STEAP3, which were involved in the regulation of immune response and cell cycle. Finally, a prognostic nomogram combining age, gender, chemotherapy, radiotherapy, IDH1 status, and the risk score model based on STEAP2 and STEAP3 was built and further validated in TCGA and Chinese Glioma Genome Atlas (CGGA) cohorts via concordance index and calibration plot, which suggested a favorable value for prognosis prediction. In conclusion, our results provided a comprehensive analysis of the STEAP family and a model for the prognosis prediction of GBM.

A Potential Mechanism of Temozolomide Resistance in Glioma-Ferroptosis

Temozolomide (TMZ) is the first-line chemotherapy drug that has been used to treat glioma for over a decade, but the benefits are limited by half of the treated patients who acquired resistance. Studies have shown that glioma TMZ resistance is a complex process with multiple factors, which has not been fully elucidated. Ferroptosis, which is a new type of cell death discovered in recent years, has been reported to play an important role in tumor drug resistance. The present study reviews the relationship between ferroptosis and glioma TMZ resistance, and highlights the role of ferroptosis in glioma TMZ resistance. Finally, the investigators discussed the future orientation for ferroptosis in glioma TMZ resistance, in order to promote the clinical use of ferroptosis induction in glioma treatment.

Recombinant human lactoferrin induces apoptosis, disruption of F-actin structure and cell cycle arrest with selective cytotoxicity on human triple negative breast cancer cells

Breast cancer is the most frequently diagnosed cancer among women worldwide. Here, recombinant human lactoferrin (rhLf) expressed in Pichia pastoris was tested for its potential cytotoxic activity on a panel of six human breast cancer cell lines. The rhLf cytotoxic effect was determined via a live-cell HTS imaging assay. Also, confocal microscopy and flow cytometry protocols were employed to investigate the rhLf mode of action. The rhLf revealed an effective CC₅₀ of 91.4 and 109.46 µg/ml on non-metastatic and metastatic MDA-MB-231 cells, with favorable selective cytotoxicity index values, 11.68 and 13.99, respectively. Moreover, rhLf displayed satisfactory SCI values on four additional cell lines, MDA-MB-468, HCC70, MCF-7 and T-47D (1.55-3.34). Also, rhLf provoked plasma membrane blebbing, chromatin condensation and cell shrinkage in MDA-MB-231 cells, being all three apoptosis-related morphological changes. Also, rhLf was able to shrink the microfilaments, forming a punctuated cytoplasmic pattern in both the MDA-MB-231 and Hs-27 cells, as visualized in confocal photomicrographs. Moreover, performing flow cytometric analysis, rhLf provoked significant phosphatidylserine externalization, cell cycle arrest in the S phase and apoptosis-induced DNA fragmentation in MDA-MB-231 cells. Hence, rhLf possesses selective cytotoxicity on breast cancer cells. Also, rhLf caused apoptosis-associated morphologic changes, disruption of F-actin cytoskeleton organization, phosphatidylserine externalization, DNA fragmentation, and arrest of the cell cycle progression on triple-negative breast cancer MDA-MB-231 cells. Overall results suggest that rhLf is using the apoptosis pathway as its mechanism to inflict cell death. Findings warranty further evaluation of rhLf as a potential anti-breast cancer drug option.

Malignant Evaluation and Clinical Prognostic Values of m6A RNA Methylation Regulators in Glioblastoma

N6-methyladenosine (m6A) RNA methylation, the most common form of mRNA modification and regulated by the m6A RNA methylation regulators ("writers," "erasers," and "readers"), has been reported to be associated with the progression of the malignant tumor. However, its role in glioblastoma (GBM) has been poorly known. This study aimed to identify the expression, potential functions, and prognostic values of m6A RNA methylation regulators in GBM. Here, we revealed that the 13 central m6A RNA methylation regulators were firmly related to the clinical and molecular phenotype of GBM. Taking advantage of consensus cluster analysis, we obtained two categories of GBM samples and found malignancy-related processes of m6A methylation regulators and compounds that specifically targeted the malignant processes. Besides, we also obtained a list of genes with poor prognosis in GBM. Finally, we derived a risk-gene signature with three selected m6A RNA methylation regulators, which allowed us to extend the in-depth study and dichotomized the OS of patients with GBM into high- and low-risk subgroups. Notably, this risk-gene signature could be used as independent prognostic markers and accurate clinicopathological parameter predictors. In conclusion, m6A RNA methylation regulators are a type of vital participant in the malignant progression of GBM, with a critical potential in the prognostic stratification and treatment strategies of GBM.

Development of sulfur doped carbon quantum dots for highly selective and sensitive fluorescent detection of Fe2+ and Fe3+ ions in oral ferrous gluconate samples

Sulfur-doped carbon quantum dots (S-CQDs) with stable blue fluorescence were synthesized through a facile one-step hydrothermal method by using ascorbic acid and thioglycolic acid as carbon and sulfur sources. The prepared S-CQDs exhibited a sensitive and selective response to Fe³⁺ ions in comparison with Fe²⁺ and other metal ions, In the presence of adequate H₂O₂, Fe²⁺ was completely transformed to Fe³⁺ that is the determinable form of iron ions, and the difference in the change of the fluorescence intensity of S-CQDs before and after adding H₂O₂ was used for detection of Fe²⁺ and Fe³⁺ ions, respectively. Under the optimum experimental conditions, the fluorescence intensity of S-CQDs gradually decreased with increasing of Fe³⁺ concentration ranging from 0 to 200 μM. Good linearity was achieved over the range of 0-200 μM. The detection limit of the developed method was 0.050 μM for Fe³⁺. The recoveries of Fe²⁺ and Fe³⁺ spiked in real samples ranged from 98.2% to 112.4%. Finally, the proposed S-CQDs integrated with Fenton system was applied to the detection of Fe²⁺ and Fe³⁺ ions in oral ferrous gluconate samples, which presents potential applications in the speciation and determination of Fe²⁺ and Fe³⁺ ions in complex samples.

64Cu-ATSM/64Cu-Cl2 and their relationship to hypoxia in glioblastoma: a preclinical study

Background

Diacetyl-bis(N4-methylthiosemicarbazone), labeled with 64Cu (⁶⁴Cu-ATSM) has been suggested as a promising tracer for imaging hypoxia. However, various controversial studies highlighted potential pitfalls that may disable its use as a selective hypoxic marker. They also highlighted that the results may be tumor location dependent. Here, we first analyzed uptake of Cu-ATSM and its less lipophilic counterpart Cu-Cl₂ in the tumor over time in an orthotopic glioblastoma model. An in vitro study was also conducted to investigate the hypoxia-dependent copper uptake in tumor cells. We then further performed a comprehensive ex vivo study to compare ⁶⁴Cu uptake to hypoxic markers, specific cellular reactions, and also transporter expression.

Methods

μPET was performed 14 days (¹⁸F-FMISO), 15 days (⁶⁴Cu-ATSM and ⁶⁴Cu-Cl2), and 16 days (⁶⁴Cu-ATSM and ⁶⁴Cu-Cl₂) after C6 cell inoculation. Thereafter, the brains were withdrawn for further autoradiography and immunohistochemistry. C6 cells were also grown in hypoxic workstation to analyze cellular uptake of Cu complexes in different oxygen levels.

Results

In vivo results showed that Cu-ASTM and Cu-Cl2 accumulated in hypoxic areas of the tumors. Cu-ATSM also stained, to a lesser extent, non-hypoxic regions, such as regions of astrogliosis, with high expression of copper transporters and in particular DMT-1 and CTR1, and also characterized by the expression of elevated astrogliosis. In vitro results show that 64Cu-ATSM showed an increase in the uptake only in severe hypoxia at 0.5 and 0.2% of oxygen while for ⁶⁴Cu-Cl2, the cell retention was significantly increased at 5% and 1% of oxygen with no significant rise at lower oxygen percentages.

Conclusion

In the present study, we show that Cu-complexes undoubtedly accumulate in hypoxic areas of the tumors. This uptake may be the reflection of a direct dependency to a redox metabolism and also a reflection of hypoxic-induced overexpression of transporters. We also show that Cu-ATSM also stained non-hypoxic regions such as astrogliosis.

Ruscogenin induces ferroptosis in pancreatic cancer cells

Pancreatic cancer is characterized by aggressive and highly metastatic phenotypes. This disease exhibits a poor patient prognosis and is considered a challenge due to the limited treatment options encountered in clinical practice. Previous studies have shown that ruscogenin, a saponin found in the root of Ophiopogon japonicus, exerts a wide range of biological functions including anticancer activity. In the present study, the effects of ruscogenin were investigated on pancreatic cancer cells and the potential molecular mechanism of this compound was explored. Cell viability was assessed using the 3-(4,5-di-2-yl)-2,5-ditetrazolium bromide (MTT) assay. Cell death was measured by trypan blue staining and by flow cytometry. The number of iron oxide nanoparticles was measured using Prussian blue staining. Reactive oxygen species (ROS) production was assessed using flow cytometry with dihydroethidium staining. Protein expression of the associated genes was assayed by western blotting. Furthermore, in vivo experiments were conducted to confirm the antitumor effects and assay the potential toxicity of ruscogenin in a nude mouse xenograft model. The results indicated that ruscogenin significantly repressed cell viability and induced cell death of pancreatic cancer cells in vitro in a dose- and time-dependent manner. Furthermore, ruscogenin increased the concentration of intracellular ferrous irons and the production of ROS. This effect was inhibited by deferoxamine (DFO). Ruscogenin induced ferroptosis by regulating the levels of transferrin and ferroportin. These two proteins were involved in ruscogenin-induced pancreatic cancer cell death. Finally, in vivo experiments demonstrated the antitumor effect of ruscogenin on pancreatic cancer xenografts in the absence of apparent toxicity. Taken collectively, the data demonstrated that ruscogenin exhibited anticancer effects in pancreatic cancer cells by inducing ferroptosis. The findings suggested that this compound may be further developed as a promising anticancer candidate for the treatment of pancreatic cancer.

Inactivation of 3-hydroxybutyrate dehydrogenase type 2 promotes proliferation and metastasis of nasopharyngeal carcinoma by iron retention

Background

3-Hydroxybutyrate dehydrogenase type 2 (BDH2) is known to catalyse a rate-limiting step in the biogenesis of the mammalian siderophore and regulate intracellular iron metabolism. Here we aim to explore the expression and possible function of BDH2 in nasopharyngeal carcinoma (NPC).

Methods

The transcription and protein expression of BDH2 in NPC were determined by both real-time RT-PCR and immunohistochemistry staining assays. Cell proliferation, migration and invasion were evaluated by MTT assay, wound-healing assay and Transwell assay, respectively. The profile of genes regulated by restoring BDH2 expression in NPC cells was analysed by cDNA microarray. The level of iron in NPC cells was detected by iron colorimetric assay.

Results

The expression of BDH2 was significantly downregulated in NPC. Ectopic expression of BDH2 inhibited NPC cell proliferation and colony formation. Meanwhile, BDH2 suppressed the migration and invasion of NPC cells by reversing the epithelial–mesenchymal transition (EMT). In addition, a higher level of BDH2 decreased the growth and metastasis of NPC cells via reducing intracellular iron level.

Conclusions

Our findings suggest that BDH2 may be a candidate tumour-suppressor gene in NPC. Decreasing intracellular iron could be an effective therapeutic approach for NPC.

Ferrous glycinate regulates cell energy metabolism by restrictinghypoxia-induced factor-1α expression in human A549 cells

Iron or oxygen regulates the stability of hypoxia inducible factor-1α (HIF-1α). We investigated whether ferrous glycinate would affect HIF-1α accumulation, aerobic glycolysis and mitochondrial energy metabolism in human A549 lung cancer cells. Incubation of A549 cells with ferrous glycinate decreased the protein levels of HIF-1α, which was abrogated by proteosome inhibitor, or prolyl hydroxylase inhibitor. The addition of ferrous glycinate decreased protein levels of glucose transporter-1, hexokinase-2, and lactate dehydrogenase A, and decreased pyruvate dehydrogenase kinase-1 (PDK-1) and pyruvate dehydrogenase (PDH) phosphorylation in A549 cells. Ferrous glycinate also increased the expression of the mitochondrial transcription factor A (TFAM), and the mitochondrial protein, cytochrome c oxidase (COX-IV). Silencing of HIF-1α expression mimicked the effects of ferrous glycinate on PDK-1, PDH, TFAM and COX-IV in A549 cells. Ferrous glycinate increased mitochondrial membrane potential and ATP production in A549 cells. These results suggest that ferrous glycinate may reverse Warburg effect through down regulating HIF-1α in A549 cells.

Role of hepcidin and iron metabolism in the onset of prostate cancer

The present study aimed to understand the roles of hepcidin and iron metabolism in the onset of prostate cancer. The prostate cancer LNCap, PC3 and DU145 cell lines were transfected with small interfering RNA (siRNA) targeting hepcidin to knockdown hepcidin expression in LNCap, PC3 and DU145 cells. The expression levels of hepcidin in prostate cancer and normal prostate RWPE-1cells were detected by western blot analysis. Exogenous hepcidin was added into the hepcidin-silenced cell lines. Intracellular iron levels were detected using a fluorescence assay, and the proliferative and migratory capacities of cells were detected using the MTT and wound-healing assays, respectively. The apoptotic rate was measured using flow cytometry, and changes in the expression of the iron-export protein ferroportin on the cell membrane were detected by western blot analysis. Hepcidin expression in prostate cancer cells was significantly higher than that of normal prostate cells (P<0.05). Furthermore, the iron levels of hepcidin-silenced cells (hepcidin^-ve groups) were significantly lower than those in the cells treated with exogenous hepcidin (hepcidin^+ve groups) (P<0.05). The proliferative capacity of the hepcidin^+ve cells significantly exceeded those of the hepcidin^-ve groups (P<0.05) and increased over time. In the wound-healing assay, the number of hepcidin^+ve cells present within the scratch sites increased compared with hepcidin^-ve cells, indicating a higher migration rate. Additionally, the expression of ferroportin in the hepcidin^-ve groups significantly exceeded that in the hepcidin^+ve groups (P<0.05). Hepcidin is involved in the onset of prostate cancer, most likely by reducing ferroportin expression and increasing intracellular iron levels to enhance the proliferation, migration and anti-apoptotic capacities of cancer cells.

Piperazinyl fragment improves anticancer activity of Triapine

A new class of TSCs containing piperazine (piperazinylogs) of Triapine, was designed to fulfill the di-substitution pattern at the TSCs N4 position, which is a crucial prerequisite for the high activity of the previously obtained TSC compounds–DpC and Dp44mT. We tested the important physicochemical characteristics of the novel compounds L¹-L¹². The studied ligands are neutral at physiological pH, which allows them to permeate cell membranes and bind cellular Fe pools more readily than less lipid-soluble ligands, e.g. DFO. The selectivity and anti-cancer activity of the novel TSCs were examined in a variety of cancer cell types. In general, the novel compounds demonstrated the greatest promise as anti-cancer agents with both a potent and selective anti-proliferative activity. We investigated the mechanism of action more deeply, and revealed that studied compounds inhibit the cell cycle (G1/S phase). Additionally we detected apoptosis, which is dependent on cell line’s specific genetic profile. Accordingly, structure-activity relationship studies suggest that the combination of the piperazine ring with Triapine allows potent and selective anticancer chelators that warrant further in vivo examination to be identified. Significantly, this study proved the importance of the di-substitution pattern of the amine N4 function.

Gallium Maltolate Disrupts Tumor Iron Metabolism and Retards the Growth of Glioblastoma by Inhibiting Mitochondrial Function and Ribonucleotide Reductase

Gallium, a metal with antineoplastic activity, binds transferrin (Tf) and enters tumor cells via Tf receptor1 (TfR1); it disrupts iron homeostasis leading to cell death. We hypothesized that TfR1 on brain microvascular endothelial cells (BMEC) would facilitate Tf-Ga transport into the brain enabling it to target TfR-bearing glioblastoma. We show that U-87 MG and D54 glioblastoma cell lines and multiple glioblastoma stem cell (GSC) lines express TfRs, and that their growth is inhibited by gallium maltolate (GaM) in vitro After 24 hours of incubation with GaM, cells displayed a loss of mitochondrial reserve capacity followed by a dose-dependent decrease in oxygen consumption and a decrease in the activity of the iron-dependent M2 subunit of ribonucleotide reductase (RRM2). IHC staining of rat and human tumor-bearing brains showed that glioblastoma, but not normal glial cells, expressed TfR1 and RRM2, and that glioblastoma expressed greater levels of H- and L-ferritin than normal brain. In an orthotopic U-87 MG glioblastoma xenograft rat model, GaM retarded the growth of brain tumors relative to untreated control (P = 0.0159) and reduced tumor mitotic figures (P = 0.045). Tumors in GaM-treated animals displayed an upregulation of TfR1 expression relative to control animals, thus indicating that gallium produced tumor iron deprivation. GaM also inhibited iron uptake and upregulated TfR1 expression in U-87 MG and D54 cells in vitro We conclude that GaM enters the brain via TfR1 on BMECs and targets iron metabolism in glioblastoma in vivo, thus inhibiting tumor growth. Further development of novel gallium compounds for brain tumor treatment is warranted. Mol Cancer Ther; 17(6); 1240-50. ©2018 AACR.